Well it's not exactly confirmed that Orochimaru transferred Shisui's Sharingan into Danzo. The main reason would have been, just like Kakashi's Sharingan, I doubt he would have wanted the strain of the Sharingan eye without the Sharingan body to wield it properly. Not to mention he wanted the best Sharingan body and eyes as were Itachi's and soon to be Sasuke's.i was thing about this from a long time
Oro was always after Sharingan
then why did he implant Uchiha Shisui's sharingan into danzo
instead he could have got Uchiha Shisui's sharingan